Could Hard Lumps On Feet Be Due To Calcium Deposits?

Hello. My husband has T1 DM, a genetic fusion in his cervical vertebrae, had a tumour removed from the area many years ago, cervical spondylosis and some nerve damage. He gets small hard lumps (approx 2mm dia) mainly in his feet that are surrounded by hard skin. The lumps come out leaving small holes. His Dr advised that these are calcium deposits due to his diabetes. He cannot find out anything else about why they are forming and if there is anything that can be done about them. Any guidance would be welcomed. Thank you. Julie